Solar Hot Water Heating Systems

Pre Heat Solar Tank System - This type of system uses two tanks The 1st tank is called a solar pre heat tank and is a basic solar hot water storage tank.  The solar pre-heat tank is used  to supplement warm water to an existing hot water tank.  This type of system is the most common retrofit as it uses the existing hot water tank and needs very little retrofit to the plumbing.   The existing main supply line is routed to the pre-heat tank and then drawn back into the supply line after it is heated. 

The most efficient systems use the basic theory of stratification.  In stratification the solar water tank is heated using thermosiphon (or a very slow pump).  This slow mixing of the water means the top layers are always the hottest.  As the top water is drawn into the main tank, the hottest water is always used 1st.   Since the average house hold used hot water in batches (not all at once), the solar system can easily supply a daily demand. 

Solar pre heat system can also be adapted to tank-less water heaters.  The principle is identical, the water is pre heated through the solar storage tank before it enters the tank-less heater.  As an example, main line water that is coming into the home at 40 degrees can be heated in a pre heat tank to say 120, if the tank-less heater is set to 140 degrees, it only has to supply 20 degrees of heat energy versus 100 degrees with outthe pre heat tank.  That is significant heat savings!

The disadvantage of this type of system may be space as a 2nd water tank is required.  A solar storage tank can be made inexpensively using and existing used or new electric hot water tank, see our information on creating a solar storage tank.

 

 Pre Heat Tank shown with optional Heat Exchanger for Glycol

 

Solar Combo Tank System - These special designed solar tanks are a combination of a solar pre-heat tank with an electric back up heater in one single unit.  This tank uses an internal heat exchange in the bottom of the tank.  The solar loop is piped through this loop and heats the water. The top of the tank contains an electric heater element to quickly top up the water temperature or aide in days of no sun.

While there are many solar pre-heat tanks with heat exchangers, there are very few that are built for the North American Market and have the proper UL certification.  In ordered to safely be installed local pluming regulations require a double vented heat exchanger with leak detection. 98% of the world wide specialty solar heaters fail to have this safety precaution.  Rheem now makes a domestic solar water heater that passes North American plumbing standards and is available in two sizes, 80 gallons and 120 gallons and comes with a 4500 Watt heater option.  Click here for more information on Rheem solar water tanks (not available in Canada).

Solar Combo tanks are ideal for new home installations however because of their relatively low demand, you will pay a premium for a specialty solar hot water tank.

 

 Solar Combo Hot Water Heater with built in Heat Exchanger

Other Solar Water Heating Articles

Solar Water Heating Vacuum Tubes

Domestic Solar Water Heating

Solar Water Heating Costs

DIY Solar Water Heating

Residential Solar Water Heating